In conventional pneumatic tires used on ice/snow roads, numerous sipes extending in the tire widthwise direction are arranged in a tread surface in which a block-based tread pattern is formed. The conventional pneumatic tires are designed to secure a better braking performance on ice from an edge effect brought about by the numerous sipes. In addition, the sipes are each formed in a three-dimensional shape. Thereby, the conventional pneumatic tires are designed: to suppress the collapse of the blocks; to thus secure a wider contact area on an ice/snow road; and to exhibit a much higher performance on ice (see Patent Document 1, for instance).
However, the formation of the numeral sipes in the tread surface inevitably entails a problem that partial wear (heel-and-toe wear) is apt to occur in the blocks, and particularly a problem that partial wear is apt to occur in blocks in shoulder regions which are subjected to heavy load during the cornering. On the other hand, enhancement of the braking performance on ice is important from the standpoint of safety on ice. Accordingly, a further improvement in the pneumatic tires has been required from the viewpoint that the braking performance on ice and the partial-wear resistance should be satisfied at the same time.